In analytical technology, sensors are known to possess individual components, which must, in the course of time, be replaced. Thus, such components can age and no longer have the desired properties. Also, certain ingredients can be depleted and must be replaced for further operation.
Examples of this are electrochemical sensors, for example, amperometric, or optical sensors. Frequently in such cases, a crucial element of the sensor, for example, a membrane, plays a deciding role. The membrane changes its chemical, physical and/or biological features in the presence of a certain substance usually corresponding to the process variable to be determined. An example of this is a membrane, which reacts sensitively to oxygen. There are, however, also other ion-selective membranes known for the most varied of substances.
The changes in the features of the membrane can be read-out, for example, optically or (electro-) chemically. For an exact determining of the process variable, it is decisive to know the characteristic properties, e.g. calibration data, of the membrane and to be able to let these enter into the determining of the process variable by a measurement transmitter or the like.
Since each batch, in the extreme case even each individual membrane, possesses different, deviating properties, the features of the membrane are usually measured at the factory and either directly written, or else input manually, into the measurement transmitter. At the latest, in the case of membrane replacement, the properties must be input manually. This is tiresome and error susceptible.
Known from U.S. Pat. No. 7,138,926 B2 is a sensor end module having a memory and at least one additional electrical component. The memory can contain features of the membrane. Since the membrane, as already mentioned, must be replaced frequently, the co-integration of an additional electrical component is expensive.
Known from DE 20 2006 007 582 U1 is a sensor end module with a fixedly connected memory. In such case, the memory must be installed already in the production of the sensor. Since, in the manufacture of the individual sensor components, partially high manufacturing temperatures occur, for example, due to glass melting, welding, etc., the memory must resist these temperatures.